DFT Study of Donor-Acceptor-Donor [1,2,5]Thiadiazolo[3,4-c]pyridine Conjugated Polymer for Solar Cell Application

Theoretical and Experimental Chemistry - Using the density functional theory (DFT) method, the electronic and optical properties of the most stable conformers of the di(selenophen-2-yl)...     

Textural,structural and catalytic behavior of low specific area silica-supported copper catalysts: effect of preparation method

Supported copper catalysts on low surface area silica were prepared by several methods and characterized by AAS, XRD, N₂ adsorption, SEM, H₂-TPR, N₂O titration, TGA-DTA, UV–Vis techniques. Their hydrogenating properties were examined in the gas-phase hydrogenation of benzaldehyde. The analysis of characterization results revealed that the choice of preparation method affected the texture, composition, and structure of the calcined and reduced Cu/SiO₂ catalysts. The dispersion and size distribution of copper species was present in different forms in the catalysts that exhibited low specific surface areas. In gas-phase hydrogenation of benzaldehyde to benzyl alcohol, the catalysts tested at the reaction temperatures of 160 and 200 °C were stable and conducted to a good catalytic activity and benzyl alcohol selectivity ranging between 5 and 39 µmol min^?1 g^?1 and 0–95%, respectively. The activity of the catalysts in gas-phase hydrogenation also depended on the particle size and the nature of copper species formed on low surface area silica.     

Facile solvent-free synthesis and structural elucidation of styrylcyclohex-2-enone derivatives

A remarkably efficient procedure for the synthesis of styrylcyclohex-2-enone derivatives at room temperature is described using a mild reaction medium consisting of lithium perchlorate and N-(trimethylsilyl)diethylamine. Several compounds of this class are synthesized conveniently and rapidly. Spectroscopic and X-ray diffraction experiments confirm the proposed structures. Correspondence: Mohammad M. Mojtahedi and Mohammad Saeed Abaee, Organic Chemistry Laboratory, Chemistry and Chemical Engineering Research Center of Iran, P.O. Box 14335-186, Tehran, Iran.     

Facile solvent-free synthesis and structural elucidation of styrylcyclohex-2-enone derivatives

A remarkably efficient procedure for the synthesis of styrylcyclohex-2-enone derivatives at room temperature is described using a mild reaction medium consisting of lithium perchlorate and N-(trimethylsilyl)diethylamine. Several compounds of this class are synthesized conveniently and rapidly. Spectroscopic and X-ray diffraction experiments confirm the proposed structures.     

High-performance liquid chromatography quantification of principal antioxidants in black seed (Nigella sativa L.) phytopharmaceuticals

A new, simple, sensitive, rapid, and accurate isocratic RP-HPLC method was developed and validated for simultaneous analysis of the principal antioxidants of Nigella sativa, i.e., thymoquinone (TQ), carvacrol (CR), and its isomer thymol (THY), in different phytopharmaceuticals. The mobile phase was water-methanol (40 + 60, v/v) at a flow rate of 1.5 mL/min. Quantification was achieved with UV detection at 254 nm, based on peak area. The method was validated for linearity, accuracy, precision, selectivity, and robustness. The proposed method is stability-indicating for determination of TQ in the presence of its degradants. The LOD and LOQ (microg/mL) were, respectively, 0.006 and 0.021 for TQ, 0.002 and 0.006 for CR, and 0.027 and 0.090 for THY. The mean recoveries measured at three concentrations were higher than 99%, with RSD <2%. This analytical method is suitable for quality control of the marker substances in this widely used natural protective and curative remedy.     

Ring transformation reactions of C-nucleosides: Facile synthesis of pyrazolo[1,5-a]pyrimidine and pyrazolo[1,5-a]triazine C-nucleosides

1,3-Dimethyluracil ( 1 ), a versatile synthon for the synthesis of various heterocycles, reacted readily with 3-aminopyrazoles 2 in sodium ethoxide to give pyrazolo[1,5-a]pyrimidines 3 . Under similar conditions, 3-aminopyrazole C-nucleosides 4 and the synthon 1 gave a mixture of pyrazolo[1,5-a]pyrimidine C-nucleosides, which was separated on a silica gel column. Attempts to remove the protecting groups yielded pyranose derivative 10 . Another synthon 1,3-dimethyl-5-azauracil and 3-aminopyrazoles 12 gave pyrazolo[1,5-a]triazines 13 . In a similar reaction with 3-aminopyrazole C-nucleosides 4 gave the corresponding pyrazolo[1,5-a]-triazine C-nucleosides 14 and 15 .